In order to reduce the amount of energy required from non-renewable energy sources, renewably energy sources, in particular solar energy, are the object of intense research. Currently a lot of effort is directed towards improving the overall conversion efficiency of a solar power system in order to make such systems ready for large-scale, commercial applications.
The basic building block of a solar power system is a so-called photovoltaic (PV) module or panel. Such PV panel may comprise many interconnected PV cells (e.g. Silicon or polymer-based PV cells connected in series and/or parallel) jointly generating about 50 W or more. The solar power system further comprises a power distribution system for effective coupling of the system to a power grid. For example, using a power distribution system, PV panels may be interconnected and arranged side-by-side, e.g. on a roof, to form a roof-integrated solar power system for domestic applications producing solar power on the order of kilowatts or more.
The power distribution system of the solar power system may comprise connection modules and cables for interconnecting the PV panels according to a predetermined electrical scheme. A connection module typically comprises one or more bypass diodes that are used to bypass a string of cells (typically in the range of 16 to 24 cells) inside a module in case one or more cells of the string are partially shaded. The power distribution system may further comprise one or more conversion modules, e.g. dc-ac converters (inverter) for conversion of the variable dc voltage output generated by one or more solar power panels into an ac current signal that is e.g. suitable for the power grid. Currently a trend is to provide each PV panel with its own electronics module comprising bypass diodes, an inverter, a dc-dc converter, a charge controller for a battery and further electronics, e.g. data exchange and monitoring electronics. Instead of a conventional bypass diode, active bypass diodes may be used. Such an active bypass diode comprises an electronic circuit providing the functionality of a diode with a very low forward voltage drop thereby providing a low power dissipation. Hence, the number of electronic components in state of the art solar power panels may increase steadily. Using such “smart” electronics modules, a power distribution system for a solar power system may be realized that allows individual control and monitoring of each PV panel in the system. Such electronics modules may comprise a protective housing and may be mounted at the back of each PV module.
As the electronics in these modules may produce heat, measures are required in order to keep the electronics below a certain temperature. These measures may include cooling structures, e.g. cooling fins, an air gap between the module and the back of the PV panel, and/or the use of thermally conductive materials such as an aluminum housing.
One example of such a module is described in US2008/0006321. The electronics module comprises an electronic switching and control unit that is in thermal contact with an cooling body comprising cooling fins in order to maintain a temperature upper limit. In more general, in conventional PV systems the heat dissipated by the electronics module mounted to the back of the PV panel is typically transported away from the PV panel towards the surrounding air using the mechanisms of convective and radiative heat transfer. At the same time, the heat transferred to the PV panel through the mechanism of heat conduction is minimized by thermally isolating the electronics from the PV module.
One problem of these known cooling schemes relates to the fact that—especially when mounted on a roof for an extended period of time—the space between the PV panel and the roof and the space between the cooling structures of the connection module may easily become clogged with dirt (e.g. twigs, leafs, etc.) thereby negatively affecting the convective and radiative transfer of heat generated by the electronic components to the surrounding air. As a consequence, the electronics in an electronics module may become too hot so that it may break down, may cause ageing effects and/or may cause drift in the electronics, thereby negatively affecting the overall conversion efficiency of the solar power system. A further problem relates to the fact that the cooling structures necessary for providing sufficient convective heat transfer are relatively complex structures, typically made out of aluminium or aluminium alloys and may thus be expensive to fabricate.
Hence there is a need in the prior art for an improved electronics assembly and/or module with an, under all circumstances, well defined thermal performance for a photovoltaic panel that is simple and low cost and provides improved operation of the electronics over an extended period of time.